Search engine providers want to present the most up-to-date information to their users. However, the Web-crawlers that are utilized to retrieve this information from Web sources retrieve content at fixed intervals regardless of how frequently the Web source content updates. Thus, a Web-crawler could visit a Web page every ten minutes but be nine minutes late in retrieving up-to-date information. On the other hand, having the Web-crawler visit the Web page too often creates other problems, such as overloading the Website and/or wasting search engine resources.